如何使用CMake在VS2017中启用/ std：c ++ 17 [英] How to enable /std:c++17 in VS2017 with CMake

问题描述

我正在尝试使用CMake将 / std：c ++ 17 编译器标志添加到VS2017中。到目前为止，我使用的是现代跨平台方式：

I'm trying to add the /std:c++17 compiler flag to VS2017 with CMake. I'm using the "modern" cross-platform way so far:

set(CMAKE_CXX_STANDARD 14)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF) # -std=c++11 instead of -std=gnu++11
set(MY_CXX_COMPILE_FEATURES cxx_generic_lambdas cxx_range_for cxx_strong_enums)

add_library(mylib INTERFACE)
target_compile_features(mylib INTERFACE ${MY_CXX_COMPILE_FEATURES})

这会增加<$ c VS2017中的$ c> / std：c ++ 14 （无论如何可能是默认值？）。
但是我在将其切换到C ++ 17时遇到了麻烦（即让它添加 / std：c ++ 17 ）。如果我只是手动添加它，则会收到不太好的警告，因为同时存在两个标志：

This adds /std:c++14 in VS2017 (which might be the default anyway?). However I'm having trouble switching this to C++17 (i.e. having it add /std:c++17). If I just add it manually, I get the not-so-nice warning because both flags are present:

1> cl：命令行警告D9025：用'/ std：c ++ 17'

$ b覆盖'/ std：c ++ 14'
$ b

我已经尝试过 set（CMAKE_CXX_STANDARD 17），但是它没有任何作用，实际上CMake文档中提到 CMAKE_CXX_STANDARD 还是对VS没有影响。

I've tried set(CMAKE_CXX_STANDARD 17) but it has no effect, in fact the CMake documentation mentions that CMAKE_CXX_STANDARD has no effect on VS anyway.

在 target_compile_features ，似乎还没有（即使在CMake-3.9.0-rc5中），即使有，我也只使用 std :: optional 来自C ++ 17，并且没有 target_compile_features 标志，这些库功能如 std :: optional 。

As for adding a C++17 feature to target_compile_features, it doesn't seem like there are any yet (even in CMake-3.9.0-rc5), and even if there were, I'm specifically only using std::optional from C++17, and there's no target_compile_features flags for library features like std::optional.

所以我的问题是，用CMake做到这一点的最好（或最丑陋）的方法是什么？并以某种方式也适用于gcc和clang？我很高兴使用最新的CMake版本（3.8或3.9）。我更喜欢它是 nice，而不是手动遍历CXX_COMPILE_FLAGS并删除字符串 / std：c ++ 14或类似的hack。

So my question is, what's the best (or least ugly) way to do this with CMake? And in a way so it'll also work for gcc and clang? I'm happy to use a very recent CMake version (3.8 or 3.9). I prefer it to be "nice" and not manually looping through CXX_COMPILE_FLAGS and removing the string "/std:c++14" or some hack like that.

（ Edit ：它也可以是VS / std：c ++ latest 开关-两者皆有可能。两者都可以使用。）

(Edit: It can also be the VS/std:c++latest switch - whichever is possible. Both work for the purpose.)

推荐答案

将我的评论变成答案

1. CMake团队正在针对VS2017（截至2017年7月，即将推出的CMake 3.10版）进行开发：

1. The CMake team is working on it for VS2017 (as for July 2017, for upcoming CMake version 3.10):

CMake：MSVC标准版本开关

那些标记似乎是相当新的开关（与该问题的日期有关）：

Those flags seem to be rather new switches (as related to the date of this question):

VS 2017 15.3预览版现在支持/ std ：c ++ 17

VS 2017 15.3 preview now supports /std:c++17

因此，对于Visual Studio，您必须手动替换或附加编译器开关，直到CMake正式支持它为止

So for Visual Studio you have to "manually" replace or append the compiler switches until CMake officially does support it.

以下是我针对 std：c ++ latest （已受支持的代码段）进行测试的代码段。在我的CMake 3.8.0版本中）：

Here is a code snippet that I've tested for std:c++latest (which is already supported e.g. in my CMake 3.8.0 version):

if (MSVC_VERSION GREATER_EQUAL "1900")
    include(CheckCXXCompilerFlag)
    CHECK_CXX_COMPILER_FLAG("/std:c++latest" _cpp_latest_flag_supported)
    if (_cpp_latest_flag_supported)
        add_compile_options("/std:c++latest")
    endif()
endif()

对于CLang和GNU，支持是从2017年开始合并到主要的源代码分支中，并且是CMake 3.8及更高版本的一部分：

For CLang and GNU the support was merged into the main source code branch begin of 2017 and is part of CMake version 3.8 and above:

CMake：功能：添加对C ++ 17语言标准的支持

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